Experimental results on the $Sigma^+(1189)$ hyperon transverse polarization in photoproduction on a hydrogen target using the CLAS detector at Jefferson laboratory are presented. The $Sigma^+(1189)$ was reconstructed in the exclusive reaction $gamma+
prightarrow K^{0}_{S} + Sigma^+(1189)$ via the $Sigma^{+} to p pi^{0}$ decay mode. The $K^{0}_S$ was reconstructed in the invariant mass of two oppositely charged pions with the $pi^0$ identified in the missing mass of the detected $ppi^+pi^-$ final state. Experimental data were collected in the photon energy range $E_{gamma}$ = 1.0-3.5 GeV ($sqrt{s}$ range 1.66-2.73 GeV). We observe a large negative polarization of up to 95%. As the mechanism of transverse polarization of hyperons produced in unpolarized photoproduction experiments is still not well understood, these results will help to distinguish between different theoretical models on hyperon production and provide valuable information for the searches of missing baryon resonances.
We have studied U+U collisions at $sqrt{s_{NN}}$ = 200 GeV using Monte Carlo Glauber, UrQMD and AMPT models. We find that it is possible to separate central tip-tip events as well as central body-body events on the basis of cuts on multiplicity and magnitude of the reduced flow vector.
